Technical Field
The present disclosure is directed to an optical device tolerant to liquid immersion.
Description of the Related Art
Optical beam shapers, either refractive or diffractive in design, are used to shape light in such a way as to generate a desired output, often with a uniform intensity distribution, although various spatial patterns are possible. An optical element of this type, for example, may be used to alter and split a single beam of light that propagates through it into several beams. A beam shaper is typically made of a single material and includes microstructures patterned directly into a surface of the material. The dimensions (i.e., height and width) of the microstructures may be customized to have a desired shaping function or output.
In general, the refractive index of a material determines the amount a light signal (i.e., light ray) will diffract or bend when propagating through the material. When the refractive index of the material is approximately equal to the refractive index of an environment immersing the material, a light signal propagating through the material will not diffract or bend. Accordingly, a shaping function or output of a beam shaper is highly dependent on having a difference between a refractive index of the material used to form the beam shaping structure and a refractive index of the environment immersing the beam shaper optic. If the refractive indices of the beam shaper optic and the immersing environment are approximately equal to each other, the beam shaper optic will lose its shaping function or output. For example, current beam shaper optics, which are commonly made of transparent polymers having a refractive index of about 1.5, often lose most of their shaping function when immersed in water, which has a refractive index of about 1.3. This is problematic for electronic devices having beam shaper optic that are used outdoors and exposed to water or rain.